Secretin releases fluid rich mainly in electrolytes and bicarbonate. Both cholecystokinin and vagal stimulation result in fluid with a high content of enzymes. Among the pancreatic enzymes, amylase and lipase are released in their active forms; whereas, the proteolytic enzymes (trypsinogen, chymotrypsinogen) are secreted as inactive zymogens. Their activation occurs in the duodenum, where the zymogens are exposed to enterokinase.